Electroplating on a truncated ball suitable for use in a typewriter

ABSTRACT

THE SURFACE OF A PLASTIC TYPEWRITER BALL IS PROCESSED IN VARIOUS SOLUTIONS IN ORDER TO PREPARE THE SURFACE TO RECEIVE A UNIFORMLY DISTRIBUTED METALLIC COATING.

May 7, 1974 M. STENE FOR USE IN A TYPEWRITER Filed Oct.

"United States Patent 'Oflice Patented May 7, 1974 U.S. Cl. 204-20 2 Claims ABSTRACT OF THE DISCLOSURE The surface of a plastic typewriter ball is processed in various solutions in order to prepare the surface to receive a uniformly distributed metallic coating.

BACKGROUND OF THE INVENTION This invention relates generally to coating plastic materials with a thin layer of metal and, more specifically to preparation of a surface of a plastic typewriter ball to receive a metal coating which is electroplated onto the surface of the typewriter ball with an improved anode design.

DESCRIPTION OF THE PRIOR ART A number of modern day typewriters utilize a truncated hollow sphere or ball which contains all the characters and numerals used in typing. In order to get the proper dynamic response, the ball is made from a lightweight material such as plastic. Plastic is preferred because of its light weight and low inertia which provides the quick response necessary for high speed typing. However, plastics do not have the required hardness and durability to withstand repeated use. Therefore, a metallic coating is placed over the interior and exterior surfaces of the plastic ball to give it the required hardness and durability.

There are numerous plastic materials that canV be utilized for the plastic ball such as melamine formaldehyde, phenolic formaldehyde and urea formaldehyde. However, urea formaldehyde is presently preferred because of its high strength, high impact resistance as well as the fact that there is a relatively close correlation of the coefficient thermal expansion of the urea formaldehyde and the nickel coating that is plated on the surface of the typewriter ball.

One of the prior art processes for preparation of the surface of the ball to receive the metallic coating is shown and described in Boggs Pat. 3,434,866. Boggs uses a solution comprised of formic acid and hydrochloric acid to prepare the surface of his ball for receiving the plating material. Still another prior art process of preparing the surface of the ball to receive a metallic coating requires Sandblasting the surface.

In my invention I have discovered an improved process and solution that enables me to prepare the surface of the ball so it tenaciously adheres to the metallic coating I plate thereon. Accordingly, a metallic coating of uniform thickness which has extremely good adhesion to the surface of the ball is an object of my invention. Another object of my invention is the utilization of a special anode for electroplating uniformly on the interior and the exterior of the hollow spherical ball.

SUMMARY OF THE INVENTION Briefly, the invention comprises an improved process for preparing the surface of a plastic ball to receive the electroplating as well as an improved anode configuration for simultaneously plating nickel onto the interior and exterior of the truncated hollow typewriter ball.

BRIEF DESCRIPTION OF THE DRAWDIG FIG. 1 shows a front elevation view partially in section of a typewriter ball being plated in an electroplating bath.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the preparation of plastic materials for plating, it is necessary to utilize numerous steps to prepare the surface for receiving the metal plating. Some of these steps are well known in the art and have been used for some time. Basically, the known procedures require the use of a solvent or wetting agent to make a plastic hydrophilic and then a conditioning or etching bath of chromic-sulphuric acid. After etching or conditioning the plastic is sensitized by the use of a stabilized stannous chloride solution which is followed by nucleation of the sensitized surface by exposure to a palladium chloride solution. This step provides a base which is used for plating the electroless nickel onto the surface. Finally, the surface is electroplated in a nickel sulfamate bath.

In my particular embodiment, I have discovered that in order to produce the desired metal coating on the urea formaldehyde ball it is necessary to use certain variations in the described process in order to produce a metal plating that will tenaciously adhere to the urea formaldehyde. Brieiiy, in my preferred process I first clean the ball in a cleaning solution. The cleaning solution is not critical. Many of the commercial available plastic cleaning solvents such as Shipley PM 900 which is manufactured and sold by Shipley Co., Inc., of Wellesley, Mass., are acceptable. The next step is to rinse the typewriter ball in deionized water for approximately one-half minute. These initial steps are conventional, however, next I subject the typewriter ball to a solution comprised of phenol, sodium hydroxide, and a wetting agent such as Tergitol NP 14 which is an ethylene oxide adduct type of wetting agent. I subject the typewriter ball to this solution for approximately two minutes at approximately C. The ball is then processed in a conventional manner by removing the ball from the solution and frinsing it in deionized water for approximately one-half minute. Next, the typewriter ball is subjected to the chromic-sulphuric acid bath at approximately C. for approximately 5% minutes. After the chromic sulphuric acid bath the ball is rinsed in deionized water for approximately one-half minute.

At this point I now provide an additional step in which I subject the ball to the phenol, sodium hydroxide and wetting agent solution again at 70 C. for approximately one minute. After subjecting the ball to the phenol, sodium hydroxide and wetting solution at 70 C. the ball is then removed and prepared for the remaining conventional processing steps prior to electroplating. The entire steps as well as subsequent conventional plating steps 3 can be best illustrated by the following typical plating cycle: l t.

PLATE CYCLE, RED UREA FORMALDEHYDE TYPEWRITER BALL Tem- pera- Time, ture, min- Step utes Shipley PM 900 (cleaning solution) 60 3 Water rinse 20 15% phenol 15% N aOH+0.3% Tergitol NP-14 60 2 (wetting agent). Water rinse 20 5,5 38% CIOs, 5% H2804 solution 70 5% v Water rinse 'Y 20 lf2 7 15% phenol, 15% NaOH solution plus .3% 70 1 wetting agent. 8 Sensitizer 1:15 H20... 20 2 9 Deionized water rinse 20 3% 10 Activate 20 2 11 Deionized water rinse 20 1 12 Electroless Ni 90 5 eter rinse 70 14 Electroplate in sulfamate solution with bro- 50 mide bath (pH 5.0).

I have discovered that the utilization of the phenol, sodium hydroxide solution in addition to the wetting agent produces a surface that tenaciously adheres to the metal coating placed on the surface. In my preferred embodiment, I use a solution containing approximately 15% benzophenol and 15 sodium hydroxide and .3% of a wetting agent. A suitable wetting agent is manufactured and sold by Union Carbide under the tradename of Tergitol NP-l4. This particular wetting agent is a nonylphenolethylene oxide adduct, however, any variety of wetting agents are suitable for use in my invention.

The particular composition of my conditioning solution of phenol, sodium hydroxide and a wetting agent is subject to wide variations from the preferred 1 to 1 ratio of phenol and sodium hydroxide. Consequently, no precise limits can be given as to the suitable and operable ranges for use in my invention. However, the strength and exposure time in the solution generally can be varied by decreasing the exposure time with higher concentration solutions. Likewise, one can increase the time for a lower concentration solution.

Referring to the lFIG. 1 reference numeral 10 generally designates my plating bath which contains a plating tank 11 and va plating solution 12. Located within plating solution 12 is a typewriter 'ball 9 which is shown in section. Located within the interior of typewriter ball 9 is an anode 13 and located on the exterior of ball 9 are anodes 14 and 15 which are suitably spaced around the exterior surface of typewriter ball 9. More anodes can l be used around the exterior surface of the ball to provide a more uniform distribution of plating on the exterior lsurface of the typewriter ball. If only two anodes are used, the ball can be periodically rotated to insure that a uniform plating is obtained. The anodes 13, 14 and 15 are connected to a common lead 16 which goes to an external power source and the type- '.writer ball 9 is connected to a lead 17 which goes to the cally, the top of anode 13 projects to within a distance h of the top of the typewriter ball. The anode can be somewhat lower but the distance h should not exceed onequarter of the dimension T of the typewriter ball. These dimensions have been found to provide uniform plating on both the interior and exterior of typewriter ball. More specifically, this prevents the build-up of plating on the edges of the ball which would interfere with the normal use of the typewriter ball. In order to arrive at a predetermined coating thickness on the interior and exterior surface of the ball, I control the time the interior or the exterior anodes are on. Typically, a suitable electroplating bath is a nickel sulfamate solution having a pH of approximately 5.0. However, no limitation is intended thereto as other nickel electroplating baths will also work.

I claim:

1. A process for preparing the surface of a polymer of urea formaldehyde to receive a metal coating by the steps of cleaning the surface of the polymer of urea formaldehyde, and etching the surface of the polymer of urea formaldehyde, activating the surface of the polymer of urea formaldehyde followed by chemical plating of the surface of the polymer of urea formaldehyde and then electroplating a metal coating on the surface of the polymer of urea formaldehyde with the improvement in the process comprising immersingvthe surface of the polymer of urea formaldehyde in a solution of approximately 15 by weight of phenol, approximately 15% by weight of sodium hydroxide and approximately .3% by weight of a wetting agent with the remainder water, followed by rinsing the surface of the polymer of urea formaldehyde and then immersing the surface of the polymer of urea formaldehyde in an acid etching bath followed by rinsing and immersing the surface of the polymer of urea formaldehyde in a solution of approximately 15% by weight of phenol, approximately 15% by weight of sodium hydroxide and approximately .3% by weight of a wetting agent with the remainder water to thereby produce a surface which will tenaciously adhere to the metal coating.

2. The process of claim 1 wherein the step of electroplating a metal layer onto the polymer of urea formaldehyde comprises electroplating a truncated typewriter ball of urea formaldehyde having a height T and an inside surface and an outside surface to be electroplated by placing a first anode within said truncated typewriter ball and a second anode outside said truncated ball with the top of said first anode and said second anode spaced at least a distance of 1A T below the top of said truncated typing ball to thereby produce an even layer of metal over the'inside surface and the outside surface of said truncated typewriter ball.

References Cited UNITED STATES PATENTS 3,547,784 12/1970 Bernhardt 204--20 3,702,286 11/1972 Ichlki 117-47 A 3,554,880 1/1971 Jenkin 204--30 3,434,866 3/1969 BOggS 117-47 A T. M. TUFARIELLO, Primary Examiner U-S. Cl. X.R. 117-47 A 

